Thermoelectric properties of Al-doped ZnO: experiment and simulation

Abstract

Advancement in doping other elements, such as Ce, Dy, Ni, Sb, In and Ga in ZnO[1], have stimulated great interest for high-temperature thermoelectric application. In this work, the effects of Al-doping in a ZnO system on the electronic structure and thermoelectric properties are presented, by experiment and calculation. Nanosized powders of Zn1−xAlxO (x = 0,0.01, 0.02, 0.03 and 0.06) were synthesized by hydrothermal method. From XRD results, all samples contain ZnO as the main phase and ZnAl2O4 (spinel phase) peaks were visible when Al additive concentrations were just 6 at%. The shape of the samples changed and the particle size decreased with increasing Al concentration. Seebeck coefficients, on the other hand, did not vary significantly. They were negative and the absolute values increased with temperature. However, the electrical resistivity decreased significantly for higher Al content. The electronic structure calculations were carried out using the open-source software package ABINIT[2], which is based on DFT. The energy band gap, density of states of Al-doped ZnO were investigated using PAW pseudopotential method within the LDA + U. The calculated density of states was then used in combination with the Boltzmann transport equation[3] to calculate the thermoelectric parameters of Al-doped ZnO. The electronic band structures showed that the position of the Fermi level of the doped sample was shifted upwards in comparison to the undoped one. After doping Al in ZnO, the energy band gap was decreased, Seebeck coefficient and electrical conductivity were increased. Finally, the calculated results were compared with the experimental results. The good agreement of thermoelectric properties between the calculation and the experimental results were obtained.

Improvement in the thermoelectric properties of porous networked Al-doped ZnO nanostructured materials synthesized via an alternative interfacial reaction and low-pressure SPS processing

“…The highest values of PF are manifested by the T-NZn 0.97 Al 0.03 OP sample (in the range of 8.45 × 10 −4 W m −1 K −2 at 325 K to 10.70 × 10 −4 W m −1 K −2 at 750 K), which are likely among or almost equivalent with the highest values of PF reported for Al-doped ZnO ceramics. 54,60,90,96 The reduction in S-values is compensated by the exceptional increase in σ, thus resulting in strikingly high PF in these porous networked Al-doped ZnO ceramics.…”

A review of thermoelectric ZnO nanostructured ceramics for energy recovery

“…The results of that investigation got the ZT value around 0.65 at 1000°C [5]. During the last decades, several studies of the thermoelectric properties of ZnO doped with either elements such as Al, Ni, Sm, Ce, Dy, Ga and Sb have been reported [1,2,19,20]. Figure 2 shows the number of articles already published between 2009 and 2017.…”

“…Among the thermoelectric materials, zinc oxide displays a good seebeck coefficient value, a high thermal stable temperature ranges and low environmental impact [22,23]. The different investigations on ZnO materials present that their thermoelectric properties can be improved by substitution with different element such as Aluminum [1][2][3][4][24][25][26][27][28], Cerium and Dysprosium [29], Gallium [6,[30][31][32], Indium [33], praseodymium [34], Antimony [20] and Nickel [7,19]. Therefore, ZnO as thermoelectric materials is slowly developing, but surely gaining attention as one of the candidates for thermoelectric applications.…”

A microwave‐based one‐pot process for homogeneous surface coating: improved electrochemical performance of Li(Ni1/3Mn1/3Co1/3)O2 with a nano‐scaled ZnO:Al layer

“…[ 18 ] The major drawback of zinc oxide is, however, its low electrical conductivity, which can be increased by orders of magnitude via doping with aluminum ions. [ 19 ]…”